The present invention relates to an internal combustion engine or pumping device and more particularly to such an engine or pumping device including one or more pistons or power elements through which energy is transferred direcily from a combustion chamber to pressurize a transmission drive fluid in a pumping chamber.
Prior art engines adapted for pressurizing a fluid to perform useful work have generally employed an engine-driven reciprocating air compressor or pump. In such prior art arrangements, the engine is connected to a compressor or pump in such a manner that power from its pistons or power elements is transferred to the compressor or pump through a complex arrangement of crankshafts, connecting rods and the like, for example. These parts, with their associated bearings, bushings, crankshaft journals and counterweights, contribute considerable mass and weight which results in a concomitant loss of efficiency. Prior art systems of this type may employ a conventional internal combustion engine, a diesel engine or even a rotary engine of the WANKEL type. Conventianal internal combustion engines are relatively unsatisfactory for such applications because they operate at relatively low compression ratios and with low efficiency, due in part to mechanical power transmission components such as those summarized above. The use of a diesel engine in such a system results in higher efficiency due both to higher compression ratios within the engine as well as ability of the engine to operate over long periods of time with reduced maintenance. However, these advantages are offset in part because of the greater weight of such engines and the continued need for transferring energy from the diesel engine to a compressor, pump or other means for performing useful work. The rotary engine in turn may also have certain advantages and disadvantages. However, it also has been used in the prior art with mechanical linkages for interconnecting te engine with suitable means for performing useful work.
Substantial effort has also been expended in the prior art to develop free-piston engines for such applications. Free-piston engines have been designed which directly connect an opposed pair of driving pistons for powering a compressor or pump. In this regard, reference is made to U.S. Pat. No. 3,432,088 issued Mar. 11, 1969; U.S. Pat. No. 2,581,600 issued Jan. 8, 1952; U.S. Pat. No. 3,031,972 issued May 1, 1962 and U.S. Pat. No. 4,115,037 issued Sept. 19, 1978. Each of these prior art references discloses an opoosed piston arrangement in engines adapted for operating compressors, pumps or the like. However, it may be seen that such free-piston engines have required relatively complex control systems in order to prevent excessive piston stroke or travel as well as to prevent excessive compression within the combustion chambers of the engines. Certain free-piston engines have also used mechanical linkages such as connecting rods, flywheels and the like for limiting piston travel and for power transmission. Other inherent difficulties for free-piston engines have related to problems of phase control or svnchronization, the need for heavy and complex auxiliary starting mechanisms and the need for precise speed control because of the mass of moving parts and high pressures. At the same time, the lack of rotary motion has made it difficult to incorporate cooling means for overcoming high temperatures developed in the engines.
Accordingly, there has been found to remain a need for an efficient engine or pumping system eliminating the need for heavy transmission means for interconnecting the engine with a compressor or pump. At the same time, a need exists for such efficient engines to be used as a prime mover in vehicles, marine propulsion units, construction machinery, electric generators and the like for performing useful work.